Constraining Theoretical Models with Astronomical and Geophysical Bounds     

Nidal Chamoun  Susana J. Landau  Hector Vucetich 《Astrophysics and Space Science》2003,283(4):595-600

We consider astronomical and geophysical bounds in order to test Kaluza-Klein like models and some particular models of Bekenstein's theory. Bounds on the free parameteres of the theories are obtained. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Heliographic longitude distribution of the flares associated with type III bursts observed at kilometric wavelengths     

Hector Alvarez  Fred T. Haddock  William H. Potter 《Solar physics》1973,31(2):493-500

We have grouped observed type III solar bursts according to the discrete frequencies of observation in the kilometric wavelength range. For each group we have obtained the bursts' frequency of occurrence as a function of the heliographic longitude of the associated optical flares. We found that flares occurring east of a certain cutoff longitude do not produce bursts observable near the earth below a given frequency. The cutoff on the west is determined by observational limitation for flares beyond the limb. The mean longitude and the extreme eastern end of the longitude distribution both shift to the west as the radio frequency decreases. We interpret these findings in terms of radio wave propagation effects and curved trajectories of the bursts' exciter particles.  相似文献   

Tropical cyclones in the Mozambique Channel: January–March 2012     

Hector Chikoore  Jan H. Vermeulen  Mark R. Jury 《Natural Hazards》2015,77(3):2081-2095

  相似文献   

Spectral Line Selection for HMI: A Comparison of Fe I 6173 Å and Ni I 6768 Å     

A. A. Norton  J. Pietarila Graham  R. K. Ulrich  J. Schou  S. Tomczyk  Y. Liu  B. W. Lites  A. López Ariste  R. I. Bush  H. Socas-Navarro  P. H. Scherrer 《Solar physics》2006,239(1-2):69-91

We present a study of two spectral lines, Fe I 6173 Å and Ni I 6768 Å, that were candidates to be used in the Helioseismic and Magnetic Imager (HMI) for observing Doppler velocity and the vector magnetic field. The line profiles were studied using the Mt. Wilson Observatory, the Advanced Stokes Polarimeter and the Kitt Peak-McMath Pierce telescope and one-meter Fourier transform spectrometer atlas. Both Fe I and Ni I profiles have clean continua and no blends that threaten instrument performance. The Fe I line is 2% deeper, 15% narrower, and has a 6% smaller equivalent width than the Ni I line. The potential of each spectral line to recover pre-assigned solar conditions is tested using a least-squares minimization technique to fit Milne-Eddington models to tens of thousands of line profiles that have been sampled at five spectral positions across the line. Overall, the Fe I line has a better performance than the Ni I line for vector-magnetic-field retrieval. Specifically, the Fe I line is able to determine field strength, longitudinal and transverse flux four times more accurately than the Ni I line in active regions. Inclination and azimuthal angles can be recovered to ≈2^° above 600 Mx cm^?2 for Fe I and above 1000 Mx cm^?2 for Ni I. Therefore, the Fe I line better determines the magnetic-field orientation in plage, whereas both lines provide good orientation determination in penumbrae and umbrae. We selected the Fe I spectral line for use in HMI due to its better performance for magnetic diagnostics while not sacrificing velocity information. The one exception to the better performance of the Fe I line arises when high field strengths combine with high velocities to move the spectral line beyond the effective sampling range. The higher g _eff of Fe I means that its useful range of velocity values in regions of strong magnetic field is smaller than Ni I.  相似文献   

Mercury levels in coral reefs along the Caribbean coast of Central America     

Guzmán HM  García EM 《Marine pollution bulletin》2002,44(12):609-1420

Sediment and coral skeleton samples from 23 coral reefs along the Caribbean coast of Costa Rica and Panama (1497 km) were evaluated for total mercury (Hg). High levels of pollution were found in the entire region with averages of 18.9 and 71.3 ppb in coral skeletons and sediments respectively. Significantly higher contamination was found in Panamanian corals (21.4 ppb) while compared to Costa Rican reef sediments (85.9 ppb). Hg from several processes and non-point sources (e.g., erosion, runoff, flooding, mining, overuse of agrochemicals, industrial waste, ports, and refineries) may have affected the entire region. The widespread observed distribution suggests that Hg is being carried along long distances within the region due to its high concentrations found in “pristine” reefs. Forest burning and colonial mining residues may be considered as possible contamination factors.  相似文献   

An assessment of metal contamination in mangrove sediments and leaves from Punta Mala Bay, Pacific Panama   总被引：5，自引：0，他引：5  

Defew LH  Mair JM  Guzman HM 《Marine pollution bulletin》2005,50(5):547-552

Due to the growing rate of urbanisation in many tropical coastal areas, there continues to be an increasing concern in relation to the impact of anthropogenic activities on mangrove forests. Punta Mala Bay is located on the Pacific coast of Panama and suffers from intense anthropogenic activities that are potentially harmful to the remaining mangrove forests. Field observations reveal that the mangrove stand within Punta Mala Bay receives high inputs of untreated domestic sewage, storm water run-off and a range of diffuse inputs from shipping activities. Results from analysis of eight metals (Mn, Cu, Zn, Ni, Pb, Fe, Cr, Cd) showed that Fe, Zn and Pb were in concentrations high enough to conclude moderate to serious contamination within the bay, and thus pose the most threat to the regeneration and growth of the mangrove. However, previous biological surveys indicate ongoing mangrove regeneration and domination of stand structure by Laguncularia racemosa, together with high numbers of seedlings and saplings.  相似文献   

Complementary use of tracer and pumping tests to characterize a heterogeneous channelized aquifer system in New Zealand     

R. L. Dann  M. E. Close  L. Pang  M. J. Flintoft  R. P. Hector 《Hydrogeology Journal》2008,16(6):1177-1191

The combined use of pumping and tracer test data enabled the derivation of equivalent average hydraulic conductivities (K_avg) for each test in a heterogeneous channelized alluvial aquifer, whereas K values of the preferential flow paths were two orders of magnitude higher. Greater and earlier drawdown was generally observed along preferential flow lines in a pumping test, within an array of 21 wells. The study aim was to characterize hydraulic properties of a channelized aquifer system in New Zealand by combining tracer and pumping test data. Estimates were able to be made of the percentage of highly permeable channels within the profile (～1.2%), effective porosity that reflected the maximum fraction of highly permeable channels within the aquifer (?_eff–pc ～0.0038), and flows through highly permeable channels (～98%) and the sandy gravel matrix material (～2%). Using ?_eff–pc, a tracer test K_avg value (～93 m/day) was estimated that was equivalent to pumping test values (～100 m/day), but two orders of magnitude smaller than K calculated solely from transport through permeable channels (K_pc ～8,400 m/day). Derived K values of permeable and matrix material were similar to values derived from grain size distribution using the Kozeny-Carman equation.  相似文献   

The role of money and the financial sector in energy-economy models used for assessing climate and energy policy     

Hector Pollitt  Jean-Francois Mercure 《Climate Policy》2018,18(2):184-197

This article outlines a critical gap in the assessment methodology used to estimate the macroeconomic costs and benefits of climate and energy policy, which could lead to misleading information being used for policy-making. We show that the Computable General Equilibrium (CGE) models that are typically used for assessing climate policy use assumptions about the financial system that sit at odds with the observed reality. These assumptions lead to ‘crowding out’ of capital and, because of the way the models are constructed, negative economic impacts (in terms of gross domestic product (GDP) and welfare) from climate policy in virtually all cases.

In contrast, macro-econometric models, which follow non-equilibrium economic theory and adopt a more empirical approach, apply a treatment of the financial system that is more consistent with reality. Although these models also have major limitations, they show that green investment need not crowd out investment in other parts of the economy – and may therefore offer an economic stimulus. Our conclusion is that improvements in both modelling approaches should be sought with some urgency – both to provide a better assessment of potential climate and energy policy and to improve understanding of the dynamics of the global financial system more generally.

POLICY RELEVANCE

This article discusses the treatment of the financial system in the macroeconomic models that are used in assessments of climate and energy policy. It shows major limitations in approach that could result in misleading information being provided to policy-makers.  相似文献   

Environmental impact in a rural community due to a lead recycling plant in Zacatecas,Mexico     

Miguel Angel Salas-Luevano  Hector Rene Vega-Carrillo 《Environmental Earth Sciences》2016,75(5):408

  相似文献   

Recognition of Space Weather Impact on the Isophot Detectors     

Hector O. Castañeda  Ulrich Klaas 《Experimental Astronomy》2000,10(2-3):369-380

The effects of changes in the space environment on the ISOPHOT photoconductivedetectors over the whole ISO mission were studied using the complete setof responsivity check measurements taken after the curing of the detectors.We found that the responsivity of the Ge-based, low bias voltage far-infrared detectors (P3, C100, and C200) is sensitive to the conditions of the Space Weather.We present evidence that an increased responsivity level (20% – 50%) after curing of the detectors is linked to the onset of geomagnetic storms. TheSi-based, high bias voltage detectors P1, P2 and PHT–SS show only small changesin their responsivity. An exception is the PHT–SL array which shows a similar,but less pronounced behaviour as the FIR detectors. While these relationshave been demonstrated by our study, a detailed physical understanding is still outstanding. The Space Weather dependent scatter of the responsivity,being the photometric scaling factor (conversion from measured photo currentto inband power on the detector), justifies the observing mode design to include frequent monitoring of its actual level.  相似文献